The mention of the "quest" appears only if the player does not have a camera in their inventory, you should have received it when you first met April. I checked the code, and re-played the relevant section of the game and did not find any errors, everything went as it should.
Do you get a similar text about the "quest" when you try to take a photo with all the possible girls in the gym (Mirko, Dexter mom, Widowmaker, Tatsumaki)? Or only with one of them?